svn commit: r208866 - head/sys/mips/mips

[Alan Cox]

Author: alc
Date: Sun Jun  6 06:07:44 2010
New Revision: 208866
URL: http://svn.freebsd.org/changeset/base/208866

Log:
  Don't set PG_WRITEABLE in init_pte_prot() (and thus pmap_enter()) unless
  the page is managed.
  
  Don't set the machine-independent layer's dirty field for the page being
  mapped in init_pte_prot().  (The dirty field is only supposed to set when
  a mapping is removed or write-protected and the page was managed and
  modified.)
  
  Determine whether or not to perform dirty bit emulation based on whether
  or not the page is managed, i.e., pageable, not based on whether the page
  is being mapped into the kernel address space.  Nearly all of the kernel
  address space consists of unmanaged pages, so this has neglible impact on
  the overhead of dirty bit emulation for the kernel address space.  However,
  there can also exist unmanaged pages in the user address space.  Previously,
  dirty bit emulation was unnecessarily performed on these pages.
  
  Tested by:	jchandra@

Modified:
  head/sys/mips/mips/pmap.c

Modified: head/sys/mips/mips/pmap.c
==============================================================================
--- head/sys/mips/mips/pmap.c	Sun Jun  6 02:36:51 2010	(r208865)
+++ head/sys/mips/mips/pmap.c	Sun Jun  6 06:07:44 2010	(r208866)
@@ -3072,26 +3072,20 @@ page_is_managed(vm_offset_t pa)
 static int
 init_pte_prot(vm_offset_t va, vm_page_t m, vm_prot_t prot)
 {
-	int rw = 0;
+	int rw;
 
 	if (!(prot & VM_PROT_WRITE))
 		rw = PTE_ROPAGE;
-	else {
-		if (va >= VM_MIN_KERNEL_ADDRESS) {
-			/*
-			 * Don't bother to trap on kernel writes, just
-			 * record page as dirty.
-			 */
-			rw = PTE_RWPAGE;
-			vm_page_dirty(m);
-		} else if ((m->md.pv_flags & PV_TABLE_MOD) ||
-		    m->dirty == VM_PAGE_BITS_ALL)
+	else if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0) {
+		if ((m->md.pv_flags & PV_TABLE_MOD) != 0)
 			rw = PTE_RWPAGE;
 		else
 			rw = PTE_CWPAGE;
 		vm_page_flag_set(m, PG_WRITEABLE);
-	}
-	return rw;
+	} else
+		/* Needn't emulate a modified bit for unmanaged pages. */
+		rw = PTE_RWPAGE;
+	return (rw);
 }
 
 /*